In the manufacture of a semiconductor device such as a large scale integrated circuit (LSI) and a very large scale integrated circuit (VLSI), or a liquid crystal display panel, a semiconductor wafer or a mother substrate for a liquid crystal display panel is irradiated with exposure light via an exposure stencil such as a photomask or a reticle, whereby a pattern of the stencil is transferred onto the surface of the wafer or the mother substrate; however, if a dust particle exists on the stencil, this particle can absorb or bend the exposure light to thereby deform the pattern or blur the edges of the pattern transferred; furthermore the underlying surface is also blackened by soiling, whereby the size, quality, appearance and the like of the semiconductor wafer or the liquid crystal display panel mother substrate are degraded. In the present invention, an “exposure stencil” shall mean a mask for lithography or a reticle.
In order to prevent these problems, the operation of exposing the substrates is generally conducted in a clean room. However, even in a clean room environment, it is not always easy to keep the exposure stencil dust-free, and hence in order to fend off the dust from the surface of the exposure stencil, a pellicle which passes exposure light well is attached to cover the exposure stencil.
In this manner, the dust is prevented from reaching the surface of the exposure stencil but can only alight on the pellicle membrane so that, if the exposure light is set to focus on the pattern of the exposure stencil, the dust on the pellicle membrane fails to shadow itself in the transferred pattern.
In general, a pellicle is manufactured by adhering a pellicle membrane to one annular face of a pellicle frame. The pellicle membrane is made of a nitrocellulose, cellulose acetate, a fluorine-containing polymer, or the like that has a high transmittance with respect to an exposure light (such as g-line, i-line, KrF excimer laser, ArF excimer laser, and F2 excimer laser). The pellicle frame is made of an aluminum alloy such as A7075, A6061, and A5052, which are black almite-anodized in the surface, or of a stainless steel or of polyethylene, etc.
The adhesion of the pellicle membrane to an annular face of the pellicle frame is effected by laying a solvent capable of dissolving the pellicle membrane on the annular face and placing the membrane over the solvent and drying the latter by air flow (ref. IP Publication 1), or by using an adhesive such as acrylic resin, epoxy resin and fluorine-containing resin (ref. IP Publications 2 and 3). Furthermore, on the other one of the two annular faces of the frame is laid a stencil-bonding agglutinant layer made of a polybutene resin, a polyvinyl acetate resin, an acrylic resin, a silicone resin or the like for attaching the pellicle frame to the exposure stencil, such as a reticle or a mask, and over this stencil-bonding agglutinant layer is laid a releasable liner for protecting the stencil-bonding agglutinant layer.
The application of the adhesive and the agglutinant to the pellicle frame is done by brush painting, spraying, dipping, squeezed-laying from a tube or a cartridge, or automatic dispensing, and the automatic dispensing is the most appropriate in that it provides quantitatively precise application. As an automatic dispenser it is possible to use a liquid application apparatus such as the ones disclosed in IP Publication 4.
A pellicle is set in a manner such that the pellicle frame entirely surrounds the pattern region formed in the surface of the exposure stencil. As the pellicle is installed for the purpose of preventing the dust from adhering to the exposure stencil, the pattern region is thereby isolated from the external atmosphere so that the dust outside the pellicle cannot reach the pattern region.
In recent years, the design rules for LSI have been modified in the direction of heightening the resolution density as high as sub-quarter micron order, and this goes hand-in-hand with shortening of the exposure light wavelength. In other words, the formerly prevalent g-line (436 nm) and i-line (365 nm) created by mercury lamps are being replaced by KrF excimer laser (248 nm), ArF excimer laser (193 nm), F2 laser (157 nm) and the like. With the increasing exposure resolution accompanied by the shortening of the wavelengths of the exposure lights, a concern being harbored anew is the fact that a warping and deformation of the pattern itself, which formerly was scarcely a problem, has become a problem in that they affect the yield of the product. The warping and deformation of the pattern is usually caused by the warping and deformation of the exposure stencil itself. And this warping and deformation of the exposure stencil is chiefly caused when the pellicle is attached to the exposure stencil.
It is known that it is the warping and deformation of the pellicle itself that renders an ill effect on the exposure stencil at the time of pellicle attachment.
A pellicle jig 5, which is a part of a pellicle kit 6 as shown in FIG. 3, is constituted by a square or rectangular frame substantially larger than a pellicle frame 1 to be handled, which is another part of the pellicle kit 6, and one pair of opposing side bars of the jig 5 are provided with jig pins 3 extending internally. Conventionally, in a pellicle manufacturing process, a pellicle frame 1 was positioned and fixed as a tapered head of a jig pin 3 was embedded in an entrance portion of a frame handling jig hole 2 (hereinafter merely referred to as “jig hole”) having a bore diameter smaller than the diameter of the jig pin 3, as shown in FIG. 2.
However, in the case of this conventional procedure of using the jig in the pellicle manufacturing process, although it was possible to fix the pellicle frame after properly positioning the pellicle frame, once the pressure by which the jig pin urges itself upon the entrance portion of the jig hole is reduced in consideration of reducing the pellicle frame distortion and deformation, the possibility of inadvertently allowing the pellicle frame to fall was not low.
Accordingly, in order to prevent such falling of the pellicle frame, it was necessary to maintain a relatively high pressure to urge the jig pin upon the pellicle frame, and as a result, the pellicle produced in such a circumstance as this tends to experience distortion and deformation in its frame, and thus the flatness of the pellicle tends to be instable.